FIGS. 1-3 show an existing design for a lock mandrel tool 10 that has an outer housing 14 with openings 16 for extendable dogs 18 shown retracted in FIG. 1. One or more seals 20 engage a seal bore in a surrounding tubular that is not shown when the tool 10 hits a no-go also not shown in the surrounding tubular. A setting sleeve 22 has a thin lower end 24 that is under the dogs 18 for run in so that dogs 18 will be retracted inside windows 16. A ramp 26 leads to a larger diameter portion 28. As seen in FIG. 2 when the ramp 26 is pushed against the dogs 18 the dogs 18 get pushed out through the windows 16 to the point where portion 28 underlies the dogs 18 and the dogs 18 are extended into a surrounding profile that is not shown. The extension of the dogs 10 raises the tool 10 off the no-go that is not shown.
Housing 14 has elongated segments 30 that define the windows 16 between them. There needs to be sufficient wall in segments 30 so that when there is a pressure differential from uphole and the dogs 18 are extended into a surrounding profile and the tool 10 as a result of dog extension is no longer supported on the no-go, that the tensile stress in the segments 30 is not exceeded. There is normally a tradeoff between making the dogs 18 wider and the need for sufficient wall thickness to tolerate the stresses administered from pressure differential. Wider dogs 18 can hold more shear load but the strength of the body is reduced when the width of segments 30 is reduced to make the dogs 18 wider.
The present invention addresses this issue in at least two ways that can be used separately or together. In one aspect the load is transferred to the dogs from the housing while avoiding or minimizing loading the window periphery and the sections of the housing that are among the windows. In another approach multiple rows of dogs are presented to share the shear loading and flexibility in the housing between rows of dogs allows the sharing of shear loading. This addresses an issue of manufacturing tolerances being high enough so that engagement of a first row of dogs can move another row of dogs into a position where they do not take the shear loading at all because they are displaced from the profile end. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.